This application relates to a temperature measuring system in a brake shoe assembly that uses a thermally conductive heat pipe to comparatively measure the temperature of the brake lining at the point of the frictionally engaging surface of the brake lining.
Most motor vehicles include a brake system having a set of brake shoe assemblies for slowing rotation of the wheels of the vehicle when the brakes are applied. Typically, each brake shoe assembly includes a brake lining material that frictionally engages a portion of a wheel of the vehicle when the brakes are applied. Such frictional contact results in the generation of heat at the frictionally engaging, or wearable, surface of the brake lining. Of course, some degree of heat generation at the wearable surface of the brake lining is expected and normal. However, an abnormal degree of heat generated is an indication of a fault in the braking mechanism.
An example of an abnormal degree of heat generation occurs in the case of a dragging brake. The brakes are applied and normal frictional engagement between the lining of the brake shoe and the wheels occurs. Once the brakes are no longer applied, the brake shoe assumes an out of service position of non-engagement with the wheel. However, a dragging brake does not fully assume an out of service position and therefore, some frictional engagement continues. Thus, an abnormal generation of heat occurs at the wearable surface of the brake lining.
Another example of an abnormal degree of heat generation may occur when comparing the wearable surface heat of the brake shoe of one wheel to that of its respective mate across the axle of a vehicle. Significant variations on temperature of the brake linings of respective wheel pairs is an indication of unbalanced wheels, or a fault in one of the braking components.
Various methods using temperature to predict lining wear, but not to measure temperature itself are disclosed in co-pending application Ser. No. 09/176,490 filed Oct. 21, 1998, entitled "Packaging A Temperature Sensing Brake Lining Wear Indicator In A Brake Shoe Assembly".
It would be desirable to provide a temperature measuring system in a brake shoe assembly that can directly measure the temperature of the brake shoe lining at its frictionally engaging, or wearable, surface. It would further be desirable to provide a system to alert a vehicle user of an abnormal temperature reading at the wearable surface of the brake shoe lining.